This fix updates the build configuration of samples/snippets pom.xml by not creating a fat jar to avoid unexpected issues and code breaks in different environments and systems.

Existing Configuration:

1. Creates a jar file spanner-google-cloud-samples-jar-with-dependencies.jar (fat jar) under target folder.
2. Samples are executed by running the following command.

java -jar target/spanner-google-cloud-samples-jar-with-dependencies.jar \
    writeusingdml test-instance example-db

Updated Configuration:

1. Creates a jar file spanner-google-cloud-samples.jar (not a fat jar) under target/spanner-snippets folder. The libraries are created in the lib folder under target/spanner-snippets.
2. With the current change, samples will be executed by running the following command.

java -jar target/spanner-snippets/spanner-google-cloud-samples.jar \
        writeusingdml test-instance example-db